For a pure SHTF gun/ammo/scenario I would limit it to common easy to get calibers that you can get in bulk. Today there isn't much out there to get in the common 5.56, 7.62 Nato, and 7.62x39. You might have better luck getting the good old .30-06, but I wouldn't count on it.

Guns to consider are the AR type, AK type, lever action type, and perhaps a good bolt gun or if money isn't an problem an M1A.

Personally I would rather have...

AR15
M1A
Winchester 94.

However if you are limited in only the two calibers you list. I would go with the 7.62 over the .30-06 even though I love the M1 and cartridge.

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